Stone me: something finally turned up! (3)
I believe the answer is:
gem
'stone' is the definition.
(thesaurus)
'me something finally turned up' is the wordplay.
'finally' suggests the final letters.
'turned up' shows that the letters should be reversed in order.
The final letter of 'something' is 'g'.
'me'+'g'='meg'
'meg' written backwards gives 'GEM'.
(Other definitions for gem that I've seen before include "Pleasant and cheerful (from German)" , "Diamond, ruby, or emerald" , "one of the Cairngorms?" , "A jewel or precious stone" , "36 Across or any other jewel" .)